还有一点:

When Lenin took over from the Czar, he treated the scientists quite well, well paid, and tolerated them for saying the wrong things.  Stalin continued this policy for some time.  Slowly, this policy was elliminated, resulting in both scientific and technological slow down.

As an example, during Korean War, Soviet airplanes could compete with American airplanes.  But by 1980s, Soviet planes were no match for American airplanes.